滨海防护林土壤氮组分对凋落物和根系去除的响应

Response of soil nitrogen pool to litter and root exclusion in costal protection forest

在亚热带滨海防护林尾巨桉、湿地松、木麻黄和纹荚相思4种人工林中,设置去除凋落物、去除根系处理,分析土壤易变性氮组分和酶活性对地上、地下碳输入减少的响应。结果显示,处理两年后,去除凋落物和根系对土壤氮组分的影响因树种而异。去除凋落物显著降低尾巨桉人工林土壤铵态氮、硝态氮、矿质氮和微生物生物量氮含量,但去除根系处理对土壤氮组分影响不显著;去除根系显著增加湿地松人工林土壤矿质氮含量;去除根系和凋落物显著降低木麻黄人工林土壤铵态氮含量;去除凋落物和根系均未显著改变纹荚相思人工林土壤氮组分含量。Pearson相关分析结果表明,土壤氮组分含量对处理的响应与β-葡萄糖苷酶、乙酰氨基葡萄糖苷酶、多酚氧化酶和过氧化物酶活性的变化有关。研究发现,来自于凋落物和根系的易变性碳输入减少,会影响微生物对氮的矿化和转化能力。在纹荚相思人工林中,微生物酶活性对去除凋落物和根系响应不敏感,表明纹荚相思人工林对易变性有机质输入的减少具有一定的适应性。

Litter and root removal trial were conducted to examine the effects of litter and root carbon input on soil labile nitrogen pool and soil enzyme activity in Eucalyptus urophylla×grandis,Pinus elliottii,Casuarina equisetifolia and Acacia aulacocarpa plantations in subtropical China.Results suggested that C input manipulation induced difference in soil labile N pool depending on tree species.After 2-year treatment,roots exclusion didn't affect soil labile N pool,but litter removal significantly reduced soil NH+4-N,NO-3-N,mineral N,and microbial biomass N concentration in E.urophylla×grandis plantation.In P.elliottii plantation,removal of roots significantly increase soil mineral N.In C.equisetifolia plantation,root or litter removal caused significant decrease in soil NH+4-N.However,there was no significant difference between the treatment and CK in soil labile N pool in A.aulacocarpa plantation.Pearson correlation analysis showed that the soil labile N change induced by litter-or root-C input might relate with soilβ-glucosidase,N-acetyl-β-d-glucosaminidase,polyphenol oxidase and peroxidase enzyme activity.Our results suggested that the reduction in litter-or root-C input may limit microbial functions in N mineralization and transformation processes.No significant response of soil enzyme activity to litter removal and root exclusion suggested a level of adjustability in ecosystem function in A.aulacocarpa plantation.